namespace System.Reactive.Linq.ObservableImpl { internal sealed class Collect<TSource, TResult> : PushToPullAdapter<TSource, TResult> { private sealed class _ : PushToPullSink<TSource, TResult> { private readonly object _gate; private readonly Func<TResult, TSource, TResult> _merge; private readonly Func<TResult, TResult> _getNewCollector; private TResult _collector; private Exception _error; private bool _hasCompleted; private bool _done; public _(Func<TResult, TSource, TResult> merge, Func<TResult, TResult> getNewCollector, TResult collector) { _gate = new object(); _merge = merge; _getNewCollector = getNewCollector; _collector = collector; } public override void OnNext(TSource value) { lock (_gate) { try { _collector = _merge(_collector, value); } catch (Exception error) { Exception ex = _error = error; Dispose(); } } } public override void OnError(Exception error) { Dispose(); lock (_gate) { _error = error; } } public override void OnCompleted() { Dispose(); lock (_gate) { _hasCompleted = true; } } public override bool TryMoveNext(out TResult current) { lock (_gate) { Exception error = _error; if (error != null) { current = default(TResult); _collector = default(TResult); error.Throw(); } else if (_hasCompleted) { if (_done) { current = default(TResult); _collector = default(TResult); return false; } current = _collector; _done = true; } else { current = _collector; try { _collector = _getNewCollector(current); } catch { Dispose(); throw; } } return true; } } } private readonly Func<TResult> _getInitialCollector; private readonly Func<TResult, TSource, TResult> _merge; private readonly Func<TResult, TResult> _getNewCollector; public Collect(IObservable<TSource> source, Func<TResult> getInitialCollector, Func<TResult, TSource, TResult> merge, Func<TResult, TResult> getNewCollector) : base(source) { _getInitialCollector = getInitialCollector; _merge = merge; _getNewCollector = getNewCollector; } protected override PushToPullSink<TSource, TResult> Run() { return new _(_merge, _getNewCollector, _getInitialCollector()); } } }